Electromechanical warning horn system

ABSTRACT

An electromechanical warning horn system comprising a hollow body ( 2 ) having a cylindrical wall ( 8 ) closed by a bottom wall ( 9 ) and a flanged edge ( 12 ), at least a bobbin ( 3 ) abutting on said bottom wall ( 9 ); an elastic membrane ( 6 ), provided with at least a mobile core ( 7 ) fixed to said flanged edge ( 12 ), at least a contact breaker ( 4 ) constituted by a support ( 22 ) and a spring ( 23 ) provided with electric contacts ( 27, 28 ), and an insulating plate ( 5 ) sandwiched between said support ( 22 ) and said spring ( 23 ), and provided with at least a layer ( 31, 32 ) of resistive silk-screen ink.

[0001] The present invention relates to an electromechanical warninghorn system.

[0002] More particularly, the present invention relates to anelectromechanical warning horn system especially suitable to be appliedon motor-vehicles.

[0003] Electromechanical warning horn systems are known that comprise ahollow body, open at an end, an electric bobbin housed within saidhollow body, and a membrane, provided with a mobile core, fixed at theedge of the open end of said hollow body.

[0004] The electric bobbin is fixed to the wall of the closed end of thehollow body and is associated to a contact breaker constituted by asupport, a spring provided with electric contacts and an insulatingplate sandwiched between said support and said spring. As is known, theelectromechanical warning horn systems of this type generate during theworking undesired electromagnetic transients.

[0005] To prevent this drawback, it has been proposed to house in thehollow body, in correspondence of special supports, a resistor ofadequate value whose ends are electrically connected to the support andthe spring of the contact breaker, resulting in this way parallel to theelectric contacts. The presence of the resistor allows to attenuate theentity of the electromagnetic transients, as it allows to cause adrastic drop of the opening and closing overvoltages of the electriccontacts.

[0006] The introduction of the resistor, while solving on the one handthe problem of the transients, is not free from further drawbacks ofboth a constructive and a functional character.

[0007] A first drawback lies in that the introduction of the resistorconstitutes a constructive complication, as it involves the presence ofelectric connections and special supports, with an ensuing increase inthe cost of the warning horn system.

[0008] A second drawback lies in that, because of the vibrations and thetemperatures deriving both from the running vehicle and the working ofsaid warning horn system, the resistor can be damaged and/or the endscan lose the electric contact which leads to malfunction.

[0009] Object of the present invention is to obviate the abovedrawbacks.

[0010] More particularly, object of the present invention is to providean electromechanical warning horn system which, besides solving theproblem of the electromagnetic transients, allows to obviate thedrawbacks of a constructive and functional character referred tohereinabove.

[0011] According to the present invention, these and still other objectsthat will be clear thanks to the following description are obtained bymeans of an electromechanical warning horn system comprising:

[0012] a hollow body whose wall comprises a first cylindrical partclosed by a bottom wall, a second flat part, a third cylindrical partand a flanged edge;

[0013] at least a bobbin abutting on said bottom wall;

[0014] an elastic membrane, provided with at least a mobile core fixedto said flanged edge of said hollow body;

[0015] at least a contact breaker comprising a support, a springprovided with electric contacts and an insulating plate sandwichedbetween said support and said spring; wherein said insulating plate isprovided with at least a layer of resistive silk-screen ink. Said atleast a layer of resistive silk-screen ink has a global resistancesuitable to eliminate the electromagnetic transients.

[0016] Said at least a layer of resistive silk-screen ink may be coatedon one, and preferably both, the surfaces of the insulating plate.

[0017] The constructive and functional characteristics of theelectromechanical warning horn system of the present invention will bebetter understood thanks to the following detailed description whereinreference is made to the attached drawings that illustrate an embodimentreported only by way of non limiting example, and wherein:

[0018]FIG. 1 shows the schematic view of a section of theelectromechanical warning horn system of the present invention,

[0019]FIG. 2 shows the schematic front view of the insulating plate ofthe warning horn system of FIG. 1;

[0020]FIG. 3 shows the schematic lateral view of the plate of FIG. 2,according to the “d” direction of FIG. 2.

[0021] With reference to the attached figures, the electromechanicalwarning horn system of the present invention, indicated by 1 as a whole,comprises a hollow body 2, an electric bobbin 3, a contact breaker 4comprising an insulating plate 5, and an elastic membrane 6 providedwith a mobile core 7.

[0022] The hollow body 2 is defined by a wall comprising a firstcylindrical part 8 closed by a bottom wall 9, a second flat part 10forming a shoulder, a third cylindrical part 11 and a lower flanged edge12. The flat part 10 is provided with a through-hole 13.

[0023] To the bottom wall 9 a supporting element 14 is associated thatis provided with a threaded pin 15 for the fastening to the vehicle anda cylindrical protrusion 16 suitable to constitute the fixed core ofbobbin 3; said threaded pin 15 and said cylindrical protrusion 16 beinglocated, respectively, on the external part and the internal part of thehollow body 2.

[0024] Bobbin 3 has a coil 17 wound on a reel 18. Reel 18 comprises acentral hole and protruding flanges 19, 20. The diameter of the centralhole is equal to the external diameter of protrusion 16; the externaldiameter of flanges 19 and 20 is substantially equal to the internaldiameter of the first cylindrical part 8 of the hollow body 2, and theheight of reel 18 is substantially equal to said first cylindrical part8.

[0025] To flange 19 there is radially associated, and forms an integralpart thereof, an extension 21, suitable to fix reel 18, and thereforebobbin 3, to the hollow body 2, in correspondence of the shoulderconstituted by the flat part 10.

[0026] The contact breaker 4 comprises a support 22, a spring 23 and theinsulating plate 5. Support 22 has a fastening zone 24 facing the flatpart 10 of the hollow body 2, and is provided with a first electriccontact 27, preferably made from tungsten. Spring 23 is constituted by alaminar element facing support 22 starting from zone 24 until it coversthe electric contact 27. At the end corresponding to the electriccontact 27, said spring 23 is provided with a second electric contact28, preferably from tungsten, mutually facing said electric contact 27.

[0027] The insulating plate 5 is sandwiched between support 22 andspring 23 and is extended, in the same way as spring 23, starting fromzone 24 of support 22 until it covers said electric contacts 27 and 28.Said insulating plate 5 has on each of the opposite surfaces 29 and 30at least a layer 31 and 32 of resistive silk-screen ink preferablycoated with an often polymeric (PTE) film technology on the respectivesurfaces 29 and 30. A hole 33 allows to connect without interruption,thank to the resistive silk-screen ink or through suitable conductivemeans, the opposite layers 31 and 32. The layers 31 and 32 of resistivesilk-screen ink are such as to provide a global electric resistancesufficient to eliminate the undesired electromagnetic transients ensuingfrom the opening and closing of the electric contacts. Preferably, saidinsulating plate 5 is constituted by bakelized cloth, and the resistivesilk-screen ink is selected from among 10 and 40Ω², preferably 22 and28Ω², while the global resistance is selected from among the values 50and 130Ω and preferably 70 and 110Ω.

[0028] For the assembly of the contact breaker 4 of theelectromechanical warning horn system of the present invention, a rivet34 is caused to pass through a base 35 from plastic material, hole 13 ofthe flat part 10 of the hollow body 2, extension 21 of reel 18, spring23, the insulating plate 5 and the fastening zone 24 of support 22.Rivet 34 is then riveted and fixes in this way bobbin 3 and the contactbreaker 4 to the hollow body 2. In this way, layers 31 and 32 ofresistive silk-screen-ink are electrically connected to the electriccontacts 27 and 28 through spring 23 and support 22 respectively, so asto constitute the electric resistance necessary to eliminate theundesired electromagnetic transients.

[0029] Membrane 6 provided with a mobile core 7 is then fixed by meansof a clinching to the flange-shaped edge 12 of the hollow body 2, tocomplete the assembly.

[0030] In resting conditions, the mobile core 7 goes away from bobbin 3,the electric contact 28 abuts, under the action of spring 23, on theelectric contact 27, so that the electric circuit of the warning hornsystem is closed and ready to be controlled.

[0031] During the running of the electromechanical warning horn systemof the present invention, when the control device is activated, theelectric circuit is complete, and therefore bobbin 3 draws the mobilecore 7, associated to membrane 6, that approaches the fixed core 16.During this movement, the mobile core 7 acts on the insulating plate 5which, in its turn, acts on spring 23, opening the electric contacts 27and 28, causing thereby the interruption of the electric circuit. Theovervoltage which generates at this moment in correspondence of theelectric contacts 27 and 28, leading even to the formation of anelectric arc, is absorbed by the resistance of layers 31 and 32 ofresistive silk-screen ink, in parallel with the electric contacts 27 and28. With the interruption of the electric circuit, bobbin 3 releases themobile core 7 and therefore membrane 6 which goes back to its startingposition, allowing in this way spring 23 to bring again the electriccontact 28 in abutment with the electric contact 27, so that a new cyclecan start.

[0032] It is now obvious that the insulating plate 5 provided withlayers 31 and 32 of resistive silk-screen ink can provide the electricresistance necessary to eliminate the unpleasant electromagnetictransients, and it is as much obvious how the drawbacks arising from theapplication of the electric resistance of the known art are overcome andeliminated.

[0033] The electromechanical warning horn system according to thepresent invention has allowed the drastic drop of the undesiredelectromagnetic transients, associated to an unusual constructivesimplicity due to the elimination of the electric resistance as anautonomous element and the elimination of the related supports. Whilethe present invention has been described in conjunction with a specificembodiment, it is obvious that many alternatives and variations will beapparent to those skilled in the art in the light of the foregoingdescription.

[0034] Accordingly, the invention is intended to embrace all of thealternatives and variations that fall within the spirit and scope of theinvention.

1. An electromechanical warning horn system comprising: a hollow body(2) whose wall comprises a first cylindrical part (8) closed by a bottomwall (9), a second flat part (10), a third cylindrical part (11) and aflanged edge (12); at least an electric bobbin (3) abutting on saidbottom wall (9); an elastic membrane ((6), provided with at least amobile core (7), fixed to said edge flange-shaped edge (12) of saidhollow body (2); at list a contact breaker (4) comprising a support(22), a spring (23) provided with electric contacts (27, 28) and aninsulating plate (5) sandwiched between said support (22) and saidspring (23) characterized in that said insulating plate (5) is providedwith at least a layer (31, 32) of resistive silk-screen ink.
 2. Theelectromechanical warning horn system according to claim 1,characterized in that the at least a layer (31, 32) of silk-screen inkhas a global resistance suitable to eliminate electromagnetictransients.
 3. The electromechanical warning horn system according toclaim 1, characterized in that the at least a layer (31, 32) ofsilk-screen ink is coated on both surfaces (29, 30) of the insulatingplate (5).
 4. The electromechanical warning horn system according toclaim 3, characterized in that the layers (31,32) coated on bothsurfaces (29, 30) of the insulating plate (5) are connected to eachother through a through-hole (33).
 5. The electromechanical warning hornsystem according to any of the preceding claims, characterized in thatsaid insulating plate (5) is preferably made from bakelized cloth. 6.The electromechanical warning horn system according to any of claims1-4, characterized in that said at least a layer (31, 32) of resistivesilk-screen ink is selected from among the values 10 and 40Ω², and theglobal resistance is selected from among the values 50 and 130Ω.
 7. Theelectromechanical warning horn system according to claim 6,characterized in that said at least one layer (31, 32) of resistivesilk-screen ink is selected from among the values of 22 and 28Ω² and hasa global resistance comprised between 70 and 110Ω.